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Water-electrolyte imbalance and endocrine disorders make the problem of maintaining patients with severe traumatic brain injury (TBI) more difficult. A plasma sodium level ≥160 mmol/l is associated with 75% mortality. The purpose of this investigation was to find the relationship between hypernatraemia and the rate of unfavorable outcomes in children with TBI.
A total of 77 children <18 years of age with TBI (admission GCS score <8) were divided retrospectively into three groups: Group A included children without hypernatraemia (n = 51), Group B children with hypernatraemia (n = 14) and Group C (n = 12) children with hypernatraemia and polyuria. Group C was considered the group of patients with central diabetes insipidus (CDI). Hypernatraemia was defined as a twice elevation of the plasma sodium level over 149 mmol/l within 24 hours, while polyuria was defined as an increase in the hourly diuresis of more than 3 ml/kg/hour in no less than 6 hours.
The mean sodium level at admission was 140.1 ± 4.1 mmol/l. Hypernatraemia was detected in 26 patients (33.8%). The mean duration of the period of hypernatraemia in Group B was 4 days (3 to 6 days), while the mean sodium level during the period of hypernatraemia was 158.3 ± 3.3 mmol/l (max 176.8 mmol/l). The duration of the period of hypernatraemia in Group C was 4.5 days with max 181.1 mmol/l and average 161 ± 4.7 mmol/l. Polyuria was diagnosed in 15.5% of the cases. The highest diuresis in this group was 4.1 mmol/kg/hour, mean 3.7 ± 0.5 ml/kg/hour. Such changes were considered a manifestation of CDI. All 12 patients in Group C received desmopressin (DDAVP) for more than 48 hours (mean 56.8 ± 4. 5 hours). The doses were 0.025 to 0.2 mg/day. In four out of 14 children in Group B (29%), an increase hourly diuresis up to 3 ml/kg/hour was considered the onset of CDI; thus, they were also prescribed DDAVP. Unfavorable outcomes (GOS score 1 to 3) during a 30-day assessment were observed only in Groups B and C. In a comparison of unsuccessful outcomes between Groups B and C, there was an increase in the unfavorable outcome rate in patients of Group C (with hypernatraemia and polyuria) - 10 children (84%) and Group B - four children (28%). The risk factor in the comparison between patients of Groups B and C was 0.3, P < 0.05.
Our results demonstrate that hypernatraemia increases the rate of unfavorable outcomes in children with TBI. Thirty-day outcomes were worse with CDI patients. Presumably, the used of DDAVP prevents dehydration and CDI advance.